Besides a WDH, sway control and brake controller, if the trailer has original tires, replace them with some quality ones. Probably LRD. Remove the brake drums and inspect the brakes and remove, inspect and repack the bearings. Inspect the suspension. Good chance the OEM plastic bushings are worn out. If you're not able to do this yourself, go to an independent RV shop. Water leakage can be the kiss of death on an RV. Read up on how to inspect caulking and check for leaks and how to do recaulking.
Learn how to set up a WDH. Very important. There is an excellent sticky in the towing forum. There are some WDHs with integral sway like Reese dual cam, Equal-i-zer and Blue Ox. Once you have the WDH properly set up, you'll love how it tows on busy interstates or twisty mountain roads.
Is anything in front end of the truck worn, what are the tires like and are the shocks in need of replacement?
Also, if you're going to be doing a lot of towing all over the place, invest in an RV GPS. A mobile hotspot like Verizon 4G along with a laptop would be a good idea so you can do things like look for a CG and check road conditions ahead of time.